Very little is known about Martin's life before the turn, though he stated that he would often watch football on Sundays and attended church regularly.
Martin is shown to be a cruel and dangerous man with a manipulative, sociopathic personality. He is shown to have the ability to talk himself out of trouble and appears to be highly intelligent. Martin appears to not be above committing cold blooded murder as shown when he nearly killed Judith in order to escape from Tyreese, and also suggesting they kill Bob after he taunted him and his group about his bite and also showed a desire to kill the members of Rick's group in the church. He is also shown to be brave to an extent as well as he shows no fear after being captured by Carol and Tyreese and before his demise, he was the only member of Gareth's group to not initially surrender to Rick and his people.
After hiding, Carol Peletier and Tyreese Williams come across a shack and Martin, who mentions Carl Grimes and Michonne as he communicates with Cynthia (another member of Terminus) while planting fireworks. Tyreese and Carol overhear this while they get the drop on Martin, binding his hands with a seat belt in the shack as she sets off to rescue the others. Martin tells Tyreese to take a car and Judith and get out of there alive. When Tyreese turns his back to Martin when a herd of walkers approach, Martin lunges towards Judith and puts his hands around her neck, threatening to break it and orders Tyreese to go outside and face the herd of walkers. Martin hears Tyreese shouting and loud thuds against the wall as he pulls out his knife and walks towards the door. Tyreese is revealed to be alive and tackles Martin to the floor, slamming his knife hand to the ground a couple of times to make him drop it. Tyreese then punches Martin several times, saying that he won't kill him. When Rick and the others show up, Tyreese tells Carol that he killed Martin because he was threatening to kill Judith.
Although Tyreese told Carol that he had killed Martin, Martin reappears after the destruction of Terminus. While Bob Stookey weeps, wandering outside the church into the surrounding forest. Martin attacks Bob and knocks him out, bringing him to a nearby camp where the remaining survivors of Terminus live. Martin can be seen among the remaining Terminus survivors cannibalizing Bob's leg along with Gareth in the final scene of this episode.
Martin continues to eat Bob's leg. As Bob starts to laugh hysterically, he stares down at him as the others get up. As Bob says that he's tainted meat, Martin doesn't react, and when Theresa asks why Gareth didn't check Bob first, Martin replies because he looked fine. Later, Martin travels along with the other Terminus to the church, after Rick leads the stronger survivors out to finish off the remaining Terminus. Martin pries open the church doors, and as they search it with the others. Gareth begins to list off the names of the hiding survivors and refers Tyreese as "Martin's good friend", while Martin grows impatient with Gareth and asks if he is done talking. As they are about to open the door where the remaining group members are hiding, Mike and Albert are shot in the head, and Gareth gets two of his fingers shot off by Rick Grimes hiding in the shadows. As Greg and Theresa surrender, Gareth tells him that he doesn't have a choice, but Martin tells him he does. Martin then notices Abraham Ford standing next to him with weapon drawn, in which he gives up and puts down his weapon. However, Rick does not let any of them go free, and as Martin tries to escape, he is pushed against the altar rail and stabbed multiple times by Tyreese's sister Sasha. Michonne retrieves her katana from Martin's backpack. Martin and the others of Gareth's group are later put down and buried by Tyreese.
Martin appears as a hallucination after Tyreese is bitten who taunts him about his impending fate, reminding him that he knew it would be him that would be killed. Martin then scolded Tyreese for not killing him, as this lead Gareth right to his group and could have saved Bob and Beth, but Bob appears and denies Martin's accusations, saying that the walker had killed him, not Martin. As Beth, Bob, Lizzie Samuels and Mika Samuels comfort Tyreese, Martin and The Governor taunt him about his fate.
This list shows the victims Martin has killed:
- Numerous counts of zombies and possibly unnamed people
After the Terminus survivors are ambushed at the church, Gareth tries getting Rick to spare them, but Rick refuses and starts to hack at Gareth with his machete, causing Martin to try and escape only to be pushed against the altar rail by Sasha and stabbed repeatedly in the chest with a knife.
- "Are we done?"
- —Martin to Gareth[src]
Martin and Gareth have a stable relationship as far as was seen. He mostly follows Gareth's orders, except when they're pinned down in the church and refused to surrender.
Martin seemed to respect Tyreese in their short time together, though it's not really known how much was the truth and how much was to get Tyreese's guard down. He also showed he was more than willing to send Tyreese out into the walkers- alone and unarmed- while threatening Judith's life to save his own life. Whatever respect he might have had for Tyreese is gone after Rick and the group destroyed Terminus as he pursued their group to kill and eat without hesitation. Martin is later one of the six people Tyreese hallucinates about during his final hours, showing that Tyreese blamed himself for Gareth's group hunting Rick's group down, and also the death of Beth Greene.
- "No Sanctuary"
- "Four Walls and a Roof"
- "What Happened and What's Going On" (Hallucination)